Practice Paper 2 (HL IB Biology)

Sucrose is formed from monosaccharides X and Y.

The diagram below shows the structure of sucrose and monosaccharide Y.

Draw and identify monosaccharide X.

The monosaccharides fructose and glucose have the same molecular formula, C₆H₁₂O₆. However, their differing structures give them different properties; for example, fructose tastes sweeter than glucose.

Suggest one advantage to the food industry of this difference.

Molecular analysis was carried out using various laboratory techniques to distinguish between samples of three different polysaccharides. Starch was separated into its constituent polysaccharides (amylose and amylopectin) before analysis. The results are shown in the table below.

The three samples were amylopectin, glycogen and amylose (not necessarily in that order).

Use your knowledge of polysaccharide structure to assign each sample to one of those three polysaccharides.

Within animal cells, fats are used as a long-term energy storage. A carbohydrate, glycogen, is used as a short-term energy storage molecule as well.

Explain the benefits of having this kind of short-term storage system.

The graph below shows the relative levels of three hormones during pregnancy.

Identify, with a reason, the hormone labelled X in the graph above.

As the woman’s body prepares to give birth, a fourth hormone, oxytocin, has an important role.

Sketch what you might expect to happen to levels of oxytocin on the graph in part a).

Note that hormone Y in the graph in part a) is progesterone.            

Oxytocin is part of a positive feedback loop during birth.

Outline the role of this positive feedback loop during birth.

Lab technicians wanted to determine the effects of light intensity and temperature on the rate of photosynthesis in rhododendron plants growing in parks and gardens. They recorded the effect of different temperatures on the net rate of photosynthesis at various light intensities. Their experiment also recorded the rate of respiration at the different temperatures. The graph below shows the results from their experiment.

Explain the increase in the net rate of photosynthesis between points A and B on the graph.

In another experiment a student looked at the effect of light intensity on the rate of photosynthesis in pond weed. They set up the investigation as shown below and altered the light intensity by changing the distance between the lamp and the pondweed.

Identify four variables that need to be controlled in this investigation.

The graph below shows the student’s results from their investigation in part b).

Calculate the percentage decrease in the rate of photosynthesis that takes place when the distance from the lamp is 10 cm compared to when it is 90 cm. Show your working.

Describe the mechanism which allows information to pass across a synapse.

Scientists wanted to investigate how a stimulating electrode changed the potential difference across an axon membrane.   The scientists inserted two other electrodes, P and Q, to record any potential difference produced. The experiment was repeated six times (A - F), using a different stimulus potential each time. The diagram below shows their results.

Explain the results of experiments A - D.

The propagation of nerve impulses is the result of local currents within the axon.

Explain how local currents are generated and how this leads to the propagation of a nerve impulse.

The diagram below shows the process of DNA replication. The horizontal lines represent the positions of bases.

Identify the parts of the DNA molecule represented by the labels W, X, Y and Z.

The table shows the percentage of different bases in the DNA of some organisms.

Calculate the missing figures for mouse DNA and complete the table.

Humans and caterpillars have very similar percentages of each base in their DNA but are not the same class of organism.

Use your knowledge of DNA structure and function to explain how this is possible.

The DNA of the virus is different from that of the human, caterpillar and mouse. Some viruses contain single-stranded DNA that is not base-paired to a complementary strand. Use data from the table in question 4b) to show evidence for this difference.

One mark is available for clarity of communication throughout this question.

MPXV is a virus that belongs in the same group as smallpox and cowpox.

Explain why viruses, such as MPXV, do not have a cell cycle.

Some cell biologists believe that the use of the term ‘cell division’ should be discontinued and replaced with ‘cell multiplication’.

Evaluate this claim using your knowledge of the cell cycle.

Human papillomaviruses are the main cause of cervical cancer.

Explain how mutagens, such as viruses, can interrupt the cell cycle to cause cancer.

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One mark is available for clarity of communication throughout this question.

Compare and contrast the X and Y chromosome.

The sex of a foetus is determined by the father.

Explain this statement.

Outline how a substitution mutation can alter the amino acid sequence of a polypeptide by using sickle cell anaemia as an example.

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